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<h1>CV and Logratio analysis</h1>

<h2>Description</h2>

<h3>Coefficient of variation (CV)</h3>

<p>
    The coefficient of variation (CV) is a normalized measure of dispersion of a
    probability distribution. It is defined as the ratio of the standard deviation
    to the mean. (<a href="http://en.wikipedia.org/wiki/Coefficient_of_variation">http://en.wikipedia.org/wiki/Coefficient_of_variation</a>)
</p>

<p>
    The advantage of the CV is that it is unitless. This allows CVs to be compared
    to each other in ways that other measures, like standard deviations or root mean
    squared residuals, cannot be.
    The standard deviations of two variables, while both measure dispersion in their
    respective variables, cannot be compared to each other in a meaningful way to
    determine which variable has greater dispersion because they may vary greatly
    in their units and the means about which they occur. The standard deviation and
    mean of a variable are expressed in the same units, so taking the ratio of these
    two allows the units to cancel.  This ratio can then be compared to other such
    ratios in a meaningful way: between two variables (that meet the assumptions
    outlined below), the variable with the smaller CV is less dispersed than the
    variable with the larger CV. (<a href="http://www.ats.ucla.edu/stat/mult_pkg/faq/general/coefficient_of_variation.htm">http://www.ats.ucla.edu/stat/mult_pkg/faq/general/coefficient_of_variation.htm</a>)
</p>


<h3>Logratio analysis</h3>
<p>
    This analysis shows a difference of each peak between two groups of samples. It is
    defined as the ratio of the natural logarithm of the ratio of each group
    average to the natural logarithm of 2:<br>
    <i>logratio = ln(groupOneAverage / groupTwoAverageg) / ln(2)</i>
</p>


<h4>Method parameters</h4>
<dl>
<dt>Peak measuring approach</dt>
<dd>It can take two values: height or area. The coefficient of variation an the logratio analisys 
    will be calculated using one of this two values. </dd>

</dl>

<h4>Screenshot of the resulting plot</h4>
<p>
CV plot:<br>
    <img src="CV.png" name="cv plot">
</p>

<p>
Logratio plot:<br>
    <img src="logratio.png" name="logratio plot">
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